Deflection Analysis Of Damaged Warship

The survivability of warship is the most important factor of the battle effectiveness . It has become more and more important as the increasing of the cost, the increasing of the amount of fuel and ammunition and the increasing of the power of weapon . In the paper, the asymmetrical beam bending theory is applied to set up damaged structural model, and under the condition of verifying and checking the longitudinal strength, the damaged warship's deflection is analysised with structural mechanics approach on the basis of elastic theory.Taking a certain warship as an example, this paper makes a discussion about the strength and deflection of the hull after its attacks by a Guided Bomb Unit and a Torpedo . On the assumption that the dimension of damaged area and the plastic region of structure have been known, according to different damaged condition, the strength and deflection of the hull under the hogging or sagging bending moments are computed respectively in two cases: One is that the damaged region is above the waterline, the other is that the damaged region is below the waterline. After the ship is attacked by a Guided Bomb Unit, the damaged position is above the waterline, the buoyancy is assumed to be unchanged, the hull deflection doesn't exceed the permitted deflection and the influence of shearing deflection on hull deflection is smaller. After the ship is attacked by a torpedo, the damaged position is under the waterline, making water enter the cabin and the external loading change. This paper calculates the ship's external loading after its body damage according to Vlasov's calculation theory. At the end of the paper, we choose the fully plastic moment as the criterion of the damaged warship's residual strength and calculate the fully plastic moment of different damaged section. Then the bending hull deflection and shearing hull deflection are calculated, and the hull deflection will perhaps exceed the permitted deflection, simultaneously the influence of latter on hull deflection is harmed. The result can be referred by some warships.